1. Technical Field
The present invention relates to a digital serial-to-parallel converter and a GaAs MMIC using the same, and more particularly, to a digital serial-to-parallel converter which may be integrated within a MMIC for controlling an RF circuit of a GaAs MMIC having excellent RF characteristics at a high frequency and a GaAs MMIC using the same.
2. Description of the Related Art
A recent antenna system has been changed from a simple/passive antenna to a complex/active antenna. Therefore, a demand for an active phased array antenna system has been rapidly increased.
The active phased array antenna requires RF components which may digitally control a magnitude and a phase of a signal.
As the recent phased array antenna needs to be small/light/cheap, a demand for a multi-function chip (MFC) in which various functions may be implemented as a single chip has been increased.
The multi-function chip is implemented as a microwave monolithic integrated chip (MMIC) using a GaAs process having excellent RF characteristics at a high frequency. The MMIC includes a digital phase shifter, a digital attenuator, a transmitting and receiving switch, and the like. These components require a large number of control lines. Due to the control lines, a chip size of the MMIC is increased and much cost is required to assemble a module or a package.
A circuit to solve the above problems is a serial-to-parallel converter. The serial-to-parallel converter is a digital circuit which serves to convert one data incoming in series into a large number of parallel data. The serial-to-parallel converter is integrated within the MMIC having an RF circuit and thus a large number of RF circuits may be controlled through a single data line, such that an interface may be very simple.
Generally, the digital circuit including the serial-to-parallel converter is implemented using a CMOS process in terms of characteristics of a FET. When the serial-to-parallel converter is implemented using a CMOS, the serial-to-parallel converter may be integrated at a small size/low power. However, characteristics of the RF circuit to be implemented within the same chip may be very deteriorate, and therefore the multi-function chip is not generally implemented using the CMOS.
As the related art, Korean Patent Application Publication No. 1998-026261 (Serial-to-Parallel Converter Using Latch Circuit) discloses that a serial-to-parallel converter is configured of circuit devices having a smaller integrated area to occupy a smaller area than that of the case in which the serial-to-parallel converter is integrated within a semiconductor chip.
As a paper disclosing a detailed internal configuration of a serial-to-parallel converter using a GaAs process which is another related art, there is “Design of MMIC Serial to Parallel Converter in Gallium Arsenide” written by Tony Nilsson and Carl Samuelsson which is a Thesis for Degree of Bachelor of Science in Engineering, Linkoping University of Sweden, on November, 2001. In the thesis, the serial-to-parallel converter is driven by a bit block which is configured of a D flip flop and an output latch. The D flip flop is implemented using a memory cell latch circuit and a circuit is configured to output both of an input and an output as a complementary signal. The complementary signal is generated by a complementary signal generator which is configured of one inverter and two NOR gates. The D flip flop circuit requires two input data and outputs two output data and therefore increases the occurrence probability of malfunction due to a complicated interface. Further, since a GaAs high electron mobility transistor (GaAs HEMT) is more sensitive to noise than the CMOS, the error probability of the output data may be increased.